Fitness

Taken too much to heart

The long accepted formula for figuring one's 'target' rate during a workout is irrelevant for most exercisers, experts say.

Anyone who has ever climbed aboard a treadmill or elliptical trainer at the gym is familiar with the little charts or electronic displays that provide information about "maximum" or "target" heart rates. The charts are supposed to tell you whether your workout is intense enough for someone your age to build a healthy heart or burn off fat.

But now exercise physiologists say that information is flawed and irrelevant for most gym rats.

The maximum heart formula has no scientific foundation, said Robert A. Robergs, director of the exercise physiology laboratories at the University of New Mexico. Rather, the formula for calculating one's maximum heart rate -- 220 minus one's age -- was based on observation and "superficial estimates," Robergs said. His research, co-written with University of New Mexico colleague Roberto Landwehr, was published last year in the Journal of Exercise Physiologyonline.

"The whole concept of a single heart-rate maximum is wrong and has been overemphasized," said Robergs, whose findings have been widely accepted among exercise physiologists since publication of the article.

For decades, the maximum-heart-rate formula has been accepted as fact by fitness buffs. Using the formula, a person can monitor the intensity of one's workout to maintain a recommended heart rate of between 60% and 80% of the maximum.

According to the formula, a 30-year-old man or woman's maximum heart rate would be 190. Thus, the heart rate for either should be between 114 and 152 during exercise. It's within this range where the greatest health benefits are bestowed, paramount among them a greatly reduced risk of heart disease.

In researching the formula's history, Robergs found no published record of research for the equation. He learned that Sid Robinson, a pioneer in exercise physiology at Indiana University and a former Olympic track athlete, experimented with various formulas for a maximum heart rate as early as 1938. After that, the formula underwent numerous revisions -- none supported by scientific data, according to Robergs.

"The formula is like saying every man is 5 foot, 10 inches," said Carl Foster, an exercise and sport science professor at the University of Wisconsin, LaCrosse. "If you happen to be one of those men, that's fine. But it's not much use otherwise.

"I think part of the reason it's hung on so long is that people like quantitative, specific guidance, and it's easy to remember," Foster said.

But Corey Cornacchio, a spokesman for heart-rate monitor manufacturer Polar Electro Inc., acknowledged the maximum-heart-rate formula isn't foolproof. Nevertheless, he said, a monitor still provides valuable information even for non-athlete exercisers because it relies on hard numbers to gauge stress and improvement.

"People, especially ones just starting out, need guidance," he said. "Even if the max heart rate is off five or six beats, it's still better than being off 20 or 30 when you can wear yourself out, or, worse, have a heart attack."

Exercise physiologists say that tests to determine an individual's maximum heart rate are, at best, only estimates. They usually produce a variety of results, which can differ as much as 10 beats per minute or more, research has shown. Tests performed on treadmills and bicycles almost always yield different conclusions, and the same fitness test done 20 minutes apart often yields conflicting data. Also, a person's diet, sleep and stress level can affect outcomes.

For everyday exercisers concerned with living longer and better, worrying about a maximum heart rate is probably a waste of time. Unless you're an athlete striving to improve performance, it simply doesn't matter, say exercise physiologists.

"I can't remember the last time I measured my heart rate," said R. James Barnard, 65, a physiological science professor at UCLA who hikes an hour a day, five times a week.

"I don't worry about pushing myself. I'm interested in my health."

Although the formula may have its limitations, the principle behind it is still scientifically sound. The question again arises, how then to gauge the workout?

Exercise physiologists increasingly recommend employing psychology to determine the worth of the workout. One method is called the Borg Perceived Exertion Scale, which is based on an exerciser's perception of how hard he or she is working. The scale ranges from 1 to 10 with each number being assigned to a corresponding feeling of fatigue. For instance, a 3 would be moderate; a 7 would be very strong.

"As simple as it sounds, it works pretty well," Foster said. "If a person falls between easy-moderate to sort of hard, they're probably right where they need to be."

The scale was devised by a Swedish scientist named Gunnar Borg in the early 1970s. Originally, the scale contained 20 points to help measure perceived exertion, but was revised in the last decade to just 10 points.

A potential downside for the Borg scale, however, is with a subject who isn't honest about the exertion level. Exercisers can be competitive people, note researchers, and sometimes for reasons of pride don't want to admit they're straining.

Another workout yardstick is what some physiologists call the "talk test." This method calls for a workout at which a person can talk comfortably -- without straining for breath -- but just barely so.

Exercise physiologists point out that choosing a method is ultimately a secondary consideration.

"The most important thing is to just get out there and do it," said Barnard. "People generally know when they're working hard enough."